192 APPLIED IMMUNOLOGY 



and require protective inoculations. Veeder's studies 

 show that in children from birth to 15 years of age, 

 which includes the period of greatest liability to diph- 

 theritic infection, approximately 50 per cent, give 

 negative reactions. If the test proves its reliability, 

 this will mean a saving of one-half of the amount of 

 antitoxin to be used prophylactically, and also a great 

 lessening in the number of cases of temporary dis- 

 ability that sometimes follows antitoxin injections. 



Kolmer and JNIoshage {Am. Jour. Dis. Child., 

 March, 1915, p. 189) , after extended studies with this 

 reaction, reach the followang conclusions: 



1. The toxin skin reaction is a valuable and reliable method for 

 detecting susceptibility to diphtheria. 



2. Persons reacting negatively to this test usually contain at least 

 ^Q unit of diphtheria antitoxin per cubic centimetre of serum, and this 

 amount of antitoxin is probably sufficient to protect against infection. 



3. Persons reacting weakly or strongly positive usually contain less 

 than %o of a unit of antitoxin per cubic centimetre of serum or none at all. 

 They may be regarded as susceptible to diphtheria and in the event of ex- 

 posure to infection should be passively immunized with antitoxin injection. 



4. About 40 to 50 per cent, of children ranging from 1 to 15 years 

 of age react positively to the toxin test; this means that the preliminary 

 use of the toxin test will eliminate the necessity of administering prophy- 

 lactic doses of antitoxin to about 50 per cent, of children. 



5. The toxin reaction indicates that the immunity conferred by an 

 injection of antitoxin begins to disappear after ten days and has gen- 

 erally passed away entirely after four weeks. 



6. The increased susceptibility of persons with scarlet fever to 

 diphtheria is shown by the toxin reaction; even after the injection of 

 antitoxin about 10 per cent, are susceptible within ten days. 



7. According to the toxin reaction the immunity conferred by an 

 attack of diphtheria is usually of short duration or entirely absent. 



8. The most practical application of the toxin reaction consists in 

 applying the test as a preliminary measure to all persons who have been 

 exposed to diphtheria and immunizing only those who react positively. 



